High dynamic range image signal generation and processing

1. An apparatus for generating an image signal in which pixels are encoded in N-bit words, the apparatus comprising:

a memory;

at least one processor coupled to the memory, the at least one processor being configured to:

decode received high dynamic range pixel values in accordance with a first color representation in M-bit words;

encode the high dynamic range pixel values in the image signal of N-bit words according to a second color representation; and

compute an indicator in the image signal of a type of high dynamic range encoding, wherein the indicator is transmitted for specifying which high dynamic range pixel values are encoded and how the high dynamic range pixel values are transformed for display.

2. The apparatus of claim 1 , wherein the first color representation is different from the second color representation.

3. The apparatus of claim 2 , wherein the at least one processor is further configured to transform the high dynamic range pixel values from the first color representation to the second color representation.

4. The apparatus of claim 2 , wherein the at least one processor is further configured to compress M-bit words into N-bit words, where M is larger than N.

5. The apparatus of claim 4 , wherein the at least one processor is further configured to use a different quantization scheme for the pixel values in accordance with the second color representation than for the pixel values in accordance with the first color representation to compress the M-bit words into the N-bit words.

6. The apparatus of claim 1 , wherein the first color representation is the same as the second color representation.

7. The apparatus of claim 1 , wherein the indicator comprises an indication of a peak white of the second color representation.

8. The apparatus of claim 1 , wherein the indicator specifies a distribution of luma or color values along a range of codeable colors in the M-bit representation along a codeable range of the N-bit signal.

9. The apparatus of claim 1 , wherein the first color representation employs a separate color value for each color component of the first color representation, and the second color representation employs a set of color values for each color component of the second color representation together with a common exponential factor.

10. The apparatus of claim 1 , wherein the image signal comprises a segment for pixel image data, and the at least one processor is further configured to alternatively include low dynamic range pixel values or the high dynamic range pixel values according to the second color representation in the segment, and the indicator specifies whether a first segment comprises low dynamic range color values or high dynamic range color values.

11. The apparatus of claim 10 , wherein the at least one processor is further configured to include a second indicator in the image signals, the second indicator stating that the segment is encoding low dynamic range pixel values both when the segment comprises low dynamic range pixel values and when the segment comprises high dynamic range pixel values.

12. The apparatus of claim 1 , wherein the at least one processor is further configured to include the high dynamic range pixel values in a Deep Color data segment according to an HDMI standard.

13. The apparatus of claim 1 , wherein the at least one processor is further configured to include the indicator in an Auxiliary Video Information InfoFrame.

14. A method of generating an image signal in which pixels are encoded in N-bit words, the method comprising:

decoding received high dynamic range pixel values in accordance with a first color representation in M-bit words;

encoding the high dynamic range pixel values in the image signal of N-bit words according to a second color representation; and

computing an indicator in the image signal of a type of high dynamic range encoding, wherein the indicator is transmitted for specifying which high dynamic range pixel values are encoded and how the high dynamic range pixel values are transformed for display.

15. An apparatus for processing an image signal, the apparatus comprising:

a memory;

at least one processor coupled to the memory, the at least one processor being configured to:

receive the image signal, a data segment of the image signal comprising one of high dynamic range pixel values in N-bit words according to a first color representation and low dynamic range pixel values according to a second color representation, and for receiving an indicator indicative of a type of high dynamic range encoding of the high dynamic range pixel values, wherein the indicator specifies which high dynamic range pixel values are encoded and how the high dynamic range pixel values are to be transformed for display;

extract data of the data segment; and

process the data of the data segment as high dynamic range pixel values dependent on the value of the indicator.

16. The apparatus as claimed in claim 15 , wherein at least one processor is configured to map the N-bit words to display renderable output signals in dependence on a coding used in the N-bit words as indicated by the indicator.

17. The apparatus as claimed in claim 15 , wherein the at least one processor is configured to apply a color transformation implementing at least a mapping of grey values along a first luminance range associated with the N-bit words, to a second luminance range associated with a display, in which the color transformation is dependent on a peak white, or any white level indication characterizing a scene luminance level of the maximum luminance codeable with the N-bits words.

18. The apparatus of claim 15 , wherein the image signal is in accordance with an HDMI standard, and the at least one processor is further configured to transmit an indication of a capability to process high dynamic range pixel values in an HDMI vendor specific data block.

19. A method of processing an image signal, the method comprising:

receiving the image signal, a data segment of the image signal comprising one of high dynamic range pixel values in N-bit words according to a first color representation and low dynamic range pixel values according to a second color representation;

receiving an indicator indicative of a type of high dynamic range encoding that specifies which high dynamic range pixel values are encoded and how the high dynamic range pixel values are transformed for display; and

processing the data of the data segment as high dynamic range pixel values or as low dynamic range pixel values dependent on the value of the indicator.